Electro-optical strand detector

ABSTRACT

In an electro-optical strand motion detecting device the improvement comprises an optically transparent tubular shield surrounding the path of said strand at said sensor.

TECHNICAL FIELD

The present invention disclosed herein provides apparatus for an improved electro-optical strand motion detection system.

BACKGROUND ART

The need for a reliable and efficient strand detection system is well known in the textile industry. Many of the prior art devices use a light source and reflected light from the strand to actuate a light sensor and provide a strand presence signal. One such prior art device is U.S. Pat. No. 4,010,908 which discloses a guide for a filament or strand and a fiber optic system for supplying light to the guide and for receiving light reflected from the strand. Other examples of using reflected light to sense the presence of a strand are shown in British Pat. Nos. 1,124,590 and 779,548.

The strand detection system disclosed in commonly assigned U.S. patent application Ser. No. 940,068 filed on Sept. 7, 1978, for Sheldon A. Canfield discloses an optical sensor unit having a solid state light source and light detector. The sensor is focused at the outer periphery of a pathway through which the strand travels.

One problem with such a system has been the build-up of fuzz around the sensor that can disable the system.

DISCLOSURE OF THE INVENTION

In an electro-optical strand sensor, the improvement comprises an optically transparent tubular shield surrounding the strand path at the sensor wherein the tubular shield is fluidically sealed at both ends to provide a partially sealed and self-cleaning electro-optical strand detection system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rear elevational view of the strand detection system according to the principles of this invention.

FIG. 2 is a sectional view of the apparatus shown in FIG. 1 taken along view 2--2.

FIG. 3 is a front elevational view of the apparatus shown in FIG. 1.

BEST MODE OF CARRYING OUT THE INVENTION

As shown in the drawings, strand detection assembly 10 contains an optical sensor or sensing means 12 which can be of the type disclosed in the aforementioned pending U.S. application Ser. No. 940,068 filed on Sept. 7, 1978, which is hereby incorporated by reference. The basic operational principles involved and corresponding electrical systems correspond to those set forth in said application.

Sensor 12 is positioned between plate or main body 14 and first member or exit block 18 with sensor 12 being located in groove 19 of block 18.

Hole 15 of plate 14 is axial aligned with aperture 20 of block 18 to form passageway 26 through which the strand passes right to left as shown in FIG. 2.

Block 18 is securely fastened to plate 14 by means of fasteners 22 and 21. Fastener 21 also serves to locate and align sensor 12 within groove 19 such that the sensor is properly focused at passageway 26 as will be explained later herein. On the opposite side of plate 14 from exit block 18, entrance block or second member 30 is securely positioned within hole 15 by any suitable conventional means such as an adhesive. Roll pin 24 serves to align blocks 18 and 30 to prevent relative rotation therebetween.

First ceramic guide eye 32 is securely located within aperture 31 of entrance block 30 by any suitable means such as an adhesive. Second ceramic guide eye 34 is also securely fastened within aperture 20 of exit block 18. Passageway 33 of first ceramic guide 32 and passageway 35 of second ceramic guide 34 are in communication with passageway 26 to permit the advancement of the strand therethrough.

Intermediate said ceramic guides 32 and 34, an optically transparent tubular shield 38 is located at the zone of focus of sensor 12 with the tubular shield 38 surrounding and defining the path along which the strand advances at that point.

Between tubular shield 38 and each of ceramic guides 32 and 34, an O-ring or fluid sealing means 36 is positioned to provide a fluidic seal for the overall passageway formed by and between the ceramic guide eyes. As shown in FIG. 2, passageway 33 is somewhat smaller than passageway 26 but it is preferred that passageway 35 be of approximately the same internal diameter as passageway 26 to provide a somewhat self-cleaning system.

With the utilization of a textile strand composed of glass filaments, it is preferred that the ceramic guides 32 and 34 be made from a material such as "Alsimag". And it has been found that shield 38 can be comprised of optical quality Pyrex having a wall thickness of 0.5 mm±0.01 mm when used in conjunction with the solid state optical sensor such as the Optron Model No. OPP-125A.

If the wall thickness is increased, for example to approximately 1 mm a more powerful sensor unit may be required for acceptable results, and the geometry of the system may have to be changed to achieve the proper focus.

Textile rovings comprised of a plurality of glass filaments generally has a binder or size coating thereon which, in addition to the other dust and particulate matter, tends to collect in the passageway of the strand detection system. Although the fuzz is generally swept away by the advancing strand according to this design, the adhesiveness of the binder may cause the binder to adhere to the wall of the tubular shield. With a fluidically sealed system as herein described, the assembly can be cleaned with a suitable solvent without contacting the sensor 12. Without the shield 38, the fuzz and binder would tend to collect within the light passageways of the sensor itself.

While in principle, the insertion of an adequately hard, transparent, and infinitesimally thin septum or shield would perform the desired task, reality requires a finite thickness to provide ruggedness. As such, it is necessary to consider the optical behavior of the shield and the dimensional relationships between the sensor, shield and passageway. The sensor 12 is positioned such that the confocal region of the illumination source and photo detector or sensor 12 falls within the bore of the tubular shield 38 and immediately adjacent or close to the wall thereof. Obviously, the shielded system, as disclosed herein, requires a slight adjustment in sensor positioning to accommodate the curved tubular wall which acts as a lens refracting the entering and emerging light rays.

The tubular material in the present instance is optical quality Pyrex to provide both adequate transparency at the operating wave length and adequate abrasion resistance at reasonable cost. Quartz, sapphire, or "hard" glass could also be used as the material for the shield depending upon factors such as abrasion resistance, cost and the like as required by the strand material involved.

As can be seen in FIG. 2, the passageways downstream of passageway 33 provide a path through the detector which has a minimum of obstruction and unevenness. Obstructions and unevenness tend to be fuzz collection points.

It is apparent within the scope of the invention modifications and different arrangements can be made other than as herein disclosed. The present disclosure is merely illustrative with the invention comprehending all variations thereof.

INDUSTRIAL APPLICABILITY

The foregoing invention is readily applicable to the glass fiber processing industry. 

We claim:
 1. In a strand sensing device having an electro-optical sensor the improvement comprising; an optically transparent tubular shield surrounding a path of strand advancement at the sensor, wherein the shield is positioned intermediate the sensor and said path and the confocal region of the sensor is located immediately adjacent the tubular shield within said shield.
 2. The device of claim 1 wherein said shield is sealed within said device to prevent fluid migration from within the device to the sensor.
 3. The device of claim 2 further comprising fluid sealing means at each end of said shield between said shield and a pair of guide eyes defining said path of strand advancement.
 4. A strand motion detection device comprising:an optical sensing means; a pair of strand guides having axially aligned passageways defining a path for said strand; an optically transparent tubular shield positioned at said sensing means having a passageway in communication with said passageways of said guides said shield being positioned intermediate said sensor and said path; and fluid sealing means intermediate said shield and said guides.
 5. The device of claims 1 or 4 wherein said sensor is of the light emitting diode type and wherein said shield material is selected from the group consisting of Pyrex, sapphire, quartz, and glass.
 6. The device of claim 4 wherein the internal diameter of one of said strand guides is substantially equal to the internal diameter of said tubular shield.
 7. The device of claim 6 wherein the other strand guide has an internal diameter substantially smaller than said tubular shield. 